The patch titled
Subject: kfence: zero guard page after out-of-bounds access
has been added to the -mm tree. Its filename is
kfence-zero-guard-page-after-out-of-bounds-access.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kfence-zero-guard-page-after-out-of-bounds-access.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kfence-zero-guard-page-after-out-of-bounds-access.patch
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------------------------------------------------------
From: Marco Elver <elver@xxxxxxxxxx>
Subject: kfence: zero guard page after out-of-bounds access
After an out-of-bounds accesses, zero the guard page before re-protecting
in kfence_guarded_free(). On one hand this helps make the failure mode of
subsequent out-of-bounds accesses more deterministic, but could also
prevent certain information leaks.
Link: https://lkml.kernel.org/r/20210312121653.348518-1-elver@xxxxxxxxxx
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kfence/core.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/kfence/core.c~kfence-zero-guard-page-after-out-of-bounds-access
+++ a/mm/kfence/core.c
@@ -371,6 +371,7 @@ static void kfence_guarded_free(void *ad
/* Restore page protection if there was an OOB access. */
if (meta->unprotected_page) {
+ memzero_explicit((void *)ALIGN_DOWN(meta->unprotected_page, PAGE_SIZE), PAGE_SIZE);
kfence_protect(meta->unprotected_page);
meta->unprotected_page = 0;
}
_
Patches currently in -mm which might be from elver@xxxxxxxxxx are
kfence-zero-guard-page-after-out-of-bounds-access.patch
